The invention relates to a mechanism for controlling a cartridge element for the purpose of controlling the flow of a fluid, for example by the use of a throttle.
In valves used for regulating paths by means of control sliders, it is known that the proportionality between a displacement of the slider, and an input signal can be obtained, by making the position of the slider dependent on an equilibrium of forces acting thereon; that means that the displacement of the slider is changed, by a change of the ratio of forces acting thereon, as the position of the slider must, according to the basic laws of physics, adjust itself, so that the forces acting thereon are in equilibrium.
By this means a precise and finely regulated position of a driven member is possible, which is, for example required in various transport machines and other devices. Using a cartridge valve, that means a valve having two inlets, but only a single control chamber, or a steering edge it has been very difficult up till now to devise a direct relation between an input signal and a dimensionally controllable cross-section for the flow of the fluid through the cartridge valve.
In contrast to slidable valves, cartridge valves have only a single input, or conduit for oil, so that it is necessary to borrow processes already established from the displacement slider technique and apply it to the cartridge technique, namely a combination of two main flow conduits and its associated piston or ring surface, with the required second conduit for oil.
By this combination the corresponding surface is exposed to any fluctuations of pressure occurring in the main conduit, which in turn requires that these fluctuations must be appropriately regulated on an oppositely diposed conduit for oil, so as to displace or position the cartridge piston to the desired position.
This type of control system makes very high demands on the quality of the regulating system.